Need help choosing flooring materials

Discussion in 'Fiberglass and Composite Boat Building' started by PPRINT, Jan 29, 2017.

  1. PPRINT
    Joined: Dec 2016
    Posts: 13
    Likes: 2, Points: 3, Legacy Rep: 10
    Location: Texas, USA

    PPRINT RobT

    Hello all.

    I am in the process of rebuilding a Mowdy S10 scooter boat (5' wide by 10' long) and have found the need to remove the floor to replace the foam and transom.

    The original floor from the manufacturer was 4mm Coremat with a single layer of fiberglass on the bottom and 2-3 layers on the top. I cannot tell exactly if the FG was CSM or a biaxial product. I can see through whatever product they used and can clearly make out the perforations in the Coremat.

    The floor is 60” wide with two 12” wide foam/fiberglass stringers so no section of the flooring will be spanning greater than 12” side to side. I have not removed the floor yet so I cannot determine if there are any bulkheads. My guess is there is not.

    I have attached a picture I found of the same model boat with the floor removed for reference.

    My quandary is what do I replace the floor with.

    The options I have come up with so far are some form of Core-Cell encapsulated in a single layer of 1708 on the bottom and 2 layers on top.

    The second option is a similar composition using balsa with the same FG plan. I prefer no wood in this boat, but if balsa is the best option I will seriously consider it.

    A third option would be to reproduce exactly what the OEM did.

    I will be using epoxy in lieu of polyester resin which ever floor is built.

    The best thing about this project is that it uses so little raw materials that the budget allows pretty much any material available and still be affordable.

    I would love to hear from others that might have input on what they would do.

    Thanks,
    Rob
     

    Attached Files:

  2. hoytedow
    Joined: Sep 2009
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    Likes: 193, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    Welcome, PPRINT.

    I know you want to avoid plywood, but if it is totally encapsulated in epoxy layered with glass weave it will give you many years of good service. I speak as an experienced amateur but gladly await the comments of the more knowledgeable professionals.
     
  3. BrettinVA
    Joined: Nov 2016
    Posts: 32
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    Location: Suffolk VA

    BrettinVA Junior Member

    I like various composites and foams for many applications. One of my primary considerations is fasteners. If you will be bolting or screwing anything to the floor using a foam core will require access on the back side of the panel in order to place large washers or backing plates. Foam/Corecell etc have poor screw retention - only the epoxy will be holding it. Coremat is better depending on how thick you use it. Marine grade wood sealed on both sides and edges is a great alternative as the hoytedow mentioned and it holds fasteners and doesn't compress. Coosa would give you the best strength if screw retention isn't an issue. Also - with using epoxy, you may only need one layer of 1708 one each side with wood or coosa.
     
  4. PPRINT
    Joined: Dec 2016
    Posts: 13
    Likes: 2, Points: 3, Legacy Rep: 10
    Location: Texas, USA

    PPRINT RobT

    hoytedow, I hear you on the ply option. Pound for pound ply is a worthy option. My only concern is keeping it encapsulated in epoxy. Years of walking on the deck by a heavy man, such as myself, and reality of things like ice chest being dropped on board by accident can lead to problems with encapsulation.

    BrettinVA, I have the same concern with fasteners, even with wood or solid fiberglass. Any perforations on a wet deck boat like this is the kiss of death in my mind. My plans are to completely finish the deck, sans finish, and then to bond synthetic wood components to the top of the deck and glassing them in. This is where the console and ice chest will mount. See attached photo of a friends boat.

    I have a question for those with working experience of epoxy. I am concerned with reproducing the OEM floor simply because I am not sure epoxy can wet down through the Core-Mat. That would not be an issue with the foam.

    I am going to call Coosa today and discuss my options with one of their application engineers.

    Thank you all,
    Rob
     

    Attached Files:

  5. hoytedow
    Joined: Sep 2009
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    Location: North of Cuba

    hoytedow Wood Butcher

    Good luck with your project. If you do ultimately use wood, make sure to seal any holes you make with 3M 5200.
     
  6. Capt.Andrew
    Joined: Feb 2017
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    Location: Texas

    Capt.Andrew New Member

    Why not use a penske board. Or a 6lb foam board with 1708 on both sides with a 1.5oz on the top for print through.
     
  7. dirtydiego41
    Joined: Jan 2017
    Posts: 29
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    Location: avila beach

    dirtydiego41 Junior Member

    There's a product called plasticore you may want to look into. As for the glass, everyone seems to be leaning on 1708 these days. 1708 is meant to be used for sheer strength, tabbing,etc. A good strong deck would be mat, roving, mat, repeat for a work deck. Mat for bonding, roving for structure, then mat for waterproofing. The way 1708 is stitched does not make for a waterproof structure down the road. Just my $.02
     

  8. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Don't over build it, it doesn't really need a core, that's why a thin Coremat worked.

    Spanning 12" is easy, what I've done before on larger spans for a walking surface is lay-up a thin glass sheet of the size needed, remove it from the mold/table surface, and then cut it to fit. It will be easy to flex and lay in place so you can get the fit right without fighting it, now glass it in place lightly.

    At this point check the strength and flex, if it's not sufficient add another layer of glass, repeat until it feels right. You could use Coremat again if you wanted, but it's probably not needed.
     
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